Visible Light Responsive Modification And Photocatalytic Properties Of BiOCl Hierarchical Microsphere

The rapid development of modern society and the economic globalization had led to a series of environmental problems.With the increasing awareness of environmental protection,scholars need to explore ways of degrading pollutants better than physical chemistry methods.Photocatalysis is a green and environment-friendly technology to purify pollutants.It can convert solar energy into chemical energy,and is stable and reusable.It is the best choice to solve environmental and energy problems at present.As a new type of semiconductor photocatalyst,BiOCl is currently the research focus of photocatalysis.Its unique layered structure and indirect optical transition mode can reduce the recombination of photogenerated carriers in the photocatalytic material,but most of the recombination phenomena of the photoelectron hole pair still exist.At the same time,the existence of the broadband gap makes it unable to respond to the visible light,the utilization efficiency of the solar energy is low and the photocatalytic performance has great space to improve.Based on the basic properties of BiOCl,the"upconversion luminescence"of carbon quantum dots?CQDs?and the"plasma resonance effect"of the novel metal Ag are proposed respectively for the modification of BiOCl,in order to further promote the optical carrier separation and improve the photocatalytic efficiency of visible light.In this paper,layered microspheres BiOCl were prepared by hydrothermal method,and Ag@BiOCl was synthesized by depositing Ag.Then,on the basis of the preparation of carbon quantum dots,the CQDs@BiOCl of doping CQDs was synthesized.In order to investigate the morphology,luminescence and photocatalytic activity of the two composite photocatalysts,a large number of characterizations were obtained and the following conclusions were obtained:?1?Pure BiOCl has a particle size of about 2?m,which is a self-assembled layered microsphere made of 40nm ultrathin nanosheets.The composite Ag@BiOCl maintained regular spherical structure and homogeneity,and the 10¹00nm Ag nanoparticles were evenly distributed on the surface of the composites.Due to the doping of Ag with SPR effect on the surface of BiOCl,the visible absorption band appears in the visible wavelength range of 360⁶00 nm.The PL pattern indicated that the recombination of light induced vectors was effectively inhibited in the system.?2?The highly monodisperse carbon quantum dots prepared by hydrothermal method are spherical structures with a particle size of about 2-4nm.CQDs was added to BiOCl as the starting material,which changed the grain size of the material.CQDs@BiOCl is a homogeneous microsphere about 1?m.The pore size is 6.95nm,and the corresponding mesoporous structure has a larger specific surface area.FTIR and EPR tests showed that oxygen groups and oxygen vacancies existed on the surface of the material.HRTEM and XPS confirmed that the carbon quantum dots have been successfully prepared.Under 450 nm visible light excitation,the upconversion effect produced high energy ultraviolet light?200nm²75nm?to stimulate BiOCl.The doping of CQDs extended the visible response range of BiOCl to 700nm,and the photocurrent test proved that the electronic transmission capacity was significantly enhanced.?3?By calculating redox potential,ESR test and scavenger experiment,the formation of free radicals of Ag@BiOCl and CQDs@BiOCl were investigated in the degradation process.The two materials have the theoretical conditions for the generation of free radicals,and the path of production and the reactive species of the reaction system are the same.Photogenerated electrons reduce adsorbed oxygen to produce·O₂^-.There are two ways to generate·OH:·O₂^-and H⁺reacted further and h⁺reacts with OH^-.Finally,by doing scavenger experiment,the main active factors involved in the photodegradation of RhB reaction system were··O₂^-and h⁺,·OH also assist the reaction.?4?The adsorption equilibrium experiment indicated that the efficiency of CQDs@BiOCl adsorbing RhB?25.5%?was much higher than that of Ag@BiOCl?19%?and BiOCl?16.9%?.The photocatalytic activity of two materials under visible light was compared and analyzed.After 180 minutes of reaction,the degradation rates of CQDs@BiOCl and Ag@BiOCl to 10mg/L RhB were 76.1%and 92.1%respectively.Comparing the results of degradation factor experiment,the efficiency of Ag@BiOCl degrades 15mg/L RhB is similar to that of CQDs@BiOCl decomposes 10mg/LRhB.0.05g Ag@BiOCl has similar decolorization effect with 0.08g CQDs@BiOCl.In conclusion,Ag@BiOCl has better photocatalytic degradation properties under visible light.